1//===-------- modsi3.S - Implement modsi3 ---------------------------------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
| 1/*===-- modsi3.S - 32-bit signed integer modulus --------------------------===//
2 *
3 * The LLVM Compiler Infrastructure
4 *
5 * This file is dual licensed under the MIT and the University of Illinois Open
6 * Source Licenses. See LICENSE.TXT for details.
7 *
8 *===----------------------------------------------------------------------===//
9 *
10 * This file implements the __modsi3 (32-bit signed integer modulus) function
11 * for the ARM architecture as a wrapper around the unsigned routine.
12 *
13 *===----------------------------------------------------------------------===*/
|
9
10#include "../assembly.h"
11
| 14
15#include "../assembly.h"
16
|
12//
13// extern int32_t __modsi3(int32_t a, int32_t b);
14//
15// Returns the remainder when dividing two 32-bit signed integers.
16// Conceptually, the function is: { return a - (a / b) * b; }
17// But if you write that in C, llvm compiles it to a call to __modsi3...
18//
19 .align 2
20DEFINE_COMPILERRT_FUNCTION(__modsi3)
21 push {r4, r5, r7, lr}
22 add r7, sp, #8 // set stack frame
23 mov r5, r0 // save a
24 mov r4, r1 // save b
25 bl ___divsi3 // compute a/b
26#if __ARM_ARCH_7A__
27 mls r0, r4, r0, r5 // mulitple result * b and subtract from a
28#else
29 // before armv7, does not have "mls" instruction
30 mul r3, r0, r4 // multiple result * b
31 sub r0, r5, r3 // a - result
32#endif
33 pop {r4, r5, r7, pc}
34
| 17#define ESTABLISH_FRAME \
18 push {r4, r7, lr} ;\
19 add r7, sp, #4
20#define CLEAR_FRAME_AND_RETURN \
21 pop {r4, r7, pc}
|
35
| 22
|
36
| 23.syntax unified
24.align 3
25DEFINE_COMPILERRT_FUNCTION(__modsi3)
26 ESTABLISH_FRAME
27 // Set aside the sign of the dividend.
28 mov r4, r0
29 // Take absolute value of a and b via abs(x) = (x^(x >> 31)) - (x >> 31).
30 eor r2, r0, r0, asr #31
31 eor r3, r1, r1, asr #31
32 sub r0, r2, r0, asr #31
33 sub r1, r3, r1, asr #31
34 // abs(a) % abs(b)
35 bl SYMBOL_NAME(__umodsi3)
36 // Apply sign of dividend to result and return.
37 eor r0, r0, r4, asr #31
38 sub r0, r0, r4, asr #31
39 CLEAR_FRAME_AND_RETURN
|
| |